b 1. Field of the Invention
The present invention relates to terminal-modified imide oligomers obtained by reacting a 2,3,3',4'-biphenyltetracarboxylic acid compound, an aromatic diamine compound and 4-(2-phenylethynyl)phthalic anhydride, and to their cured products.
Composite materials obtained as cured products by heat curing fiber-reinforced prepregs whose matrix resins are terminal-modified imide oligomers according to the present invention have excellent heat resistance and mechanical properties, and are particularly suitable for use in devices for the aeronautical and space industries.
2. Description of the Related Art
Cured products of terminal-modified imide oligomers exhibit excellent heat resistance and have long been known as matrix resins for molded products and fiber-reinforced composite materials.
As examples of such terminal-modified imide oligomers, Japanese Unexamined Patent Publication No. 64-54029 describes terminal-modified imide oligomers obtained by reacting a 2,3,3',4'-biphenyltetracarboxylic acid compound, an aromatic diamine compound and an unsaturated dicarboxylic acid such as nadic anhydride or an unsaturated monoamine compound such as propargylamine; Japanese Unexamined Patent Publication No. 64-54030 describes terminal-modified imide oligomers obtained by reacting a 3,3',4,4'-biphenyltetracarboxylic acid compound, an aromatic diamine compound and an unsaturated dicarboxylic acid such as nadic anhydride or an unsaturated monoamine compound such as propargylamine; and Japanese Unexamined Patent Publication No. 3-292130 describes a process for producing molded products of terminal-modified imide oligomers obtained by reacting a biphenyltetracarboxylic acid compound, an aromatic diamine compound and an unsaturated dicarboxylic acid such as maleic anhydride or an unsaturated monoamine compound such as propargylamine.
These terminal-modified imide oligomers modified with unsaturated monoamine compounds and terminal-modified imide oligomers modified with nadic anhydride all have low heat resistance as cured products.
There have recently been proposed, therefore, terminal-modified imide oligomers modified with 4-(phenylethynyl)phthalic anhydride.
For example, terminal-modified imide oligomers which are oligomers of 1,4-diaminobenzene and 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride and are terminal-modified with 4-(phenylethynyl)phthalic anhydride are described in "Polymer", 35, 4865 (1994), and terminal-modified imide oligomers obtained by reacting 3,3',4,4'-biphenyltetracarboxylic dianhydride, 1,1,1,3,3,3-hexafluoro-2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, p-phenylenediamine and 4-(phenylethynyl)phthalic anhydride are described in "Polymer", 35, 4874 (1994).
However, these publicly known terminal-modified imide oligomers make use of special compounds as the essential aromatic tetracarboxylic dianhydrides.